Tempest fine wire spark plugs

[Fly Boomer]

5 minutes ago, exM20K said:

My last mag rebuild lasted between 0 and 4 hours this year.  Big fan of the fine wire plugs.

-dan

Of course we would like to know what kind of mags, and who did the rebuild.

[exM20K]

S6RSC-25P would have to check paperwork for the shop.  

[Fly Boomer]

11 minutes ago, exM20K said:

S6RSC-25P would have to check paperwork for the shop.  

I don't think I need an overhaul, but upcoming annual will tell.  It's nice to have reports for both good  service and bad .

[PT20J]

Aircraft Magneto Service does excellent work. They quit doing the dual Bendix mags though.

[geoffb]

29 minutes ago, PT20J said:

Aircraft Magneto Service does excellent work. They quit doing the dual Bendix mags though.

They did two pressurized Bendix mags for me in January in 2 days.  Had cores on the shelf.  Not the cheapest, but excellent service and they have a solid reputation.  Only about 25 hours in, so can't comment on quality from personal experience yet.

 

 

Edited April 28, 2023 by geoffb

[Fly Boomer]

On 4/28/2023 at 11:17 AM, PT20J said:

Aircraft Magneto Service does excellent work. They quit doing the dual Bendix mags though.

I noticed that on their web site the other day.  Mine are the Bendix 1200s so not a problem.  Thanks for the tip.

[T. Peterson]

On 4/27/2023 at 7:24 PM, EricJ said:

It used to be pretty normal to run fine wires on the bottom and massives on top.    This is what I've done for a long time, and it has worked pretty well.   The fine wires on the bottom resist lead fouling, which I had trouble with with the bottom massives.    I've had zero fouling issues since putting the fine wires in the bottom.    In my experience they do seem to last longer than the massives in the top spots.

A two part question: Why do you run massives on top? Is it an operational reason or do FW’s on top just not make sense economically?

Part 2: Is this something that I ought to consider in my 1979 231k, or is it more geared to the larger engines in the later Mooneys.

[Ragsf15e]

2 hours ago, T. Peterson said:

A two part question: Why do you run massives on top? Is it an operational reason or do FW’s on top just not make sense economically?

Part 2: Is this something that I ought to consider in my 1979 231k, or is it more geared to the larger engines in the later Mooneys.

I’m guessing here for @EricJ, but the lower plugs are easier to foul as they are on the bottom of the cylinder.  Fine wires are better at resisting fouling.  Massives on top because they are cheaper and fouling isn’t an issue.  He’s running an io-360.

 

[Will.iam]

5 hours ago, T. Peterson said:

A two part question: Why do you run massives on top? Is it an operational reason or do FW’s on top just not make sense economically?

Part 2: Is this something that I ought to consider in my 1979 231k, or is it more geared to the larger engines in the later Mooneys.

Torrey I experienced easier starts and smoother idling when i switched from champion. I also measured the resistance of the champions and none of them were in spec. I. E. All of them were over 5k ohms with 2 over 500k ohms and one over 2million ohms!

 

[T. Peterson]

30 minutes ago, Will.iam said:

Torrey I experienced easier starts and smoother idling when i switched from champion. I also measured the resistance of the champions and none of them were in spec. I. E. All of them were over 5k ohms with 2 over 500k ohms and one over 2million ohms!

 

Thank you Will. Did you do the FW thing on the bottom and Massives on top?

First I have to get my ridiculous oil leak fixed. Plane is going to DM tomorrow.

[M20F]

I just filed my massives down till the wire was really fine, works great at a 10th of the price!

[EricJ]

4 hours ago, Ragsf15e said:

I’m guessing here for @EricJ, but the lower plugs are easier to foul as they are on the bottom of the cylinder.  Fine wires are better at resisting fouling.  Massives on top because they are cheaper and fouling isn’t an issue.  He’s running an io-360.

 

Yeah, that's pretty much it.   There's a small benefit of just the technical/logistical diversity, too, but that's not that big of a deal.

[philiplane]

mixing fine wires and massives eliminates the ability to rotate them, which is critical to get the longest life from the plugs. Rotation from the top to bottom, and next in firing order is needed to change the polarity that the plug sees from the magneto. 

[T. Peterson]

1 hour ago, M20F said:

I just filed my massives down till the wire was really fine, works great at a 10th of the price!

You almost had me till I saw Rags laughing!!

[carusoam]

Early on…. There were two issues…

1) Fine Wires were new technology, with not much track record…

2) Cost.

the benefits…

3) FWs are much better at surviving and punching through the crud that collects in the bottom plug hole…  oil drips and lead balls tend to collect there.

4) fuel/air mixture has an easier time circulating through the gap where the spark emits.

 

Over time…

5) The old technology were Champion massives that suffered from the variable resistance… and horrible customer support.

6) a Tempest welding issue allowed the center electrode to escape on the FWs…

7) Everyone is now familiar with checking the resistance of the Champions…

8) Manufacturing process updates quickly solved the escaping center electrode issue…

 

Sooo… 

9) it was normal to put the FWs in the bottom… 

10) Does anyone go completely FW?

 

Next challenge or opportunity…. Old Mags spark on every engine rotation… generating a wasted spark for each useful spark for the power stroke…

Other quirks… half of the sparks run from the center to the outside, where the other half is running from the outside to the center… hence the reason for swapping plugs in a particular order….

11) Do the new Electronic mags avoid the wasted spark?

12) Do the new electronic mags have the same spark direction quirk?

 

13) unfortunately It isn’t physically possible to allow a Champion plug to wear out until it is a fine wire….  The automatic increase in resistance occurs faster than the wear issue…   

 

PP thoughts only,  I may have confused things a bit…

Best regards,

-a-

[A64Pilot]

Fine wire plugs aren’t nearly as new as we think, in fact many if not most “new” things for piston engines our Grandfathers knew about and was normal ops for them, like LOP for example

http://www.enginehistory.org/Operations/R-4360Ops/r-4360ops1.shtml

Ignition System: 4 Scintilla S14RN-15 low tension magnetos mounted on the propeller reduction gear case, 56 Transformer Coils (2 mounted on the top of each cylinder) and 56 fine-wire spark plugs. The magneto gear drive mechanism permitted the Flight Engineer to select either 20° or 30° spark advance magneto-to-engine timing. The 30° selection was limited to cruise power settings only.

I went through WOEC “Warrant Officer Entry Course” with an old National Guard guy that had been a Crew Chief on a B-36, he said it took a squad of men pulling a wagon full of 336 plugs to change plugs in a B-36, took them most of the day.